A word Canadians use to ensure the other person is following along with the conversation. Not often used between Canadians themselves, but used excessively when visiting the USA and explaining things about Canada.

Dumbass – So is that near Vancouver?
Torontonian – No, Vancouver is on the West Coast near Seattle.
Dumbass – Seattle!! you shittin' me?.
Torontonian – No really eh, Toronto is close to Buffalo.
Dumbass – Buffalo!!
Torontonian – Where you from Eh?
Dumbass – North Tonawanda, New Yew York.
Torontonian –Eh, you’re like 10 miles from the border.
Dumbass – You mean the US border?
Torontonian – I’d love to talk but I have talk to those hot chicks from Chicago at the shooter bar. Nice talk’n to you eh?

it just means you dont give either way. when you say it you fling your hand either up or down, depending on the context in which you are saying it. eh! said as a short sound means you dont care, but if you enlongate it and say it more slowly with a downwards action of the hand it generally means you can't be bothered to do something (whatever the person asked you about)

short version:
male: do you want to have sex?
female: eh!

long version:
mother:are you going to go to work on your homework project tonight?
kid:eeeeeeeeeh!